Italian Patent No. 208921 discloses a quick-connect and disconnect fitting for water system piping. One advantage, among many, of this fitting is that it can be quickly and easily unscrewed from the pipe to which it is attached, unlike all previous models which were difficult to disconnect to the extent that, in similar circumstances, the pipe was cut close to the joint, and if the joint was to be re-used, the end of the pipe that remained in the joint had to be removed, an elaborate and troublesome task.
The invention that is disclosed in Italian Patent No. 208921 consists of a joint with a hollow cylindrical body. The hole in the body where the pipe is inserted is of a larger bore than the external diameter of the pipe, so that it can house a sleeve with an internal diameter that exactly matches that of the exterior of the tube. There is a ring of flexible tabs at the end of the sleeve, that are created by deep diametric cuts at regular intervals in the front end of the sleeve. The interior of the cylindrical cavity that houses the aforementioned sleeve and in which it can move has a number of tightening ribs and its front end is a ring like truncated cone-shaped shoulder. This shoulder connects the aforementioned cavity to an intermediate section of the tube with a smaller diameter, which in turn ends in a ring-shaped step, beyond which there is the tube whose diameter is precisely the same as the internal diameter of the pipe, and which projects from the other end of the body of the joint; the opposite end to that in which the pipe is inserted.
It should be pointed out that truncated cone-shaped shoulder at the end of the section of tube in which the aforementioned sleeve is housed and can move, has its narrow end facing the sleeve, and thus towards the entrance to the joint. Therefore, when the sleeve is pushed forward as far as it will go, all the flexible tabs are stretched apart by the truncated cone-shaped surface against which the aforementioned tabs are pressed.
When the sleeve is extracted from its housing, the aforementioned tightening ribs in the housing exert an action which is completely the opposite of that of the truncated cone-shaped shoulder, and exert a centripetal pressure on the external backs of the tabs, causing the tabs to bend towards the interior, and the tabs tend to lock together towards the center thus permitting the complete extraction of the sleeve when there is no pipe present which would otherwise obstruct the tabs from bending sufficiently towards the center to permit the sleeve to be removed from the joint.
On the contrary, in the last of the two above cases, the teeth can on the internal side of the flexible tabs bite into the external surface of the pipe with ever increasing force, thus preventing the pipe from being removed while the system is operating, even when subject to a great deal of tractive force.
The pipe is, however, easy and quick to disconnect, when the sleeve is held in one hand in a fully forward position, and the pipe is pulled back by the other. In this case, the pipe is no longer externally locked in place by the teeth on the tabs, which are now held in an open position by the truncated cone-shaped surface against which they are pressed while the sleeve is held pressed in a fully forward position.
During the use of the aforementioned quick connect and disconnect joint, it has however been found that the biting action of the teeth on the internal side of the aforementioned flexible tabs is not always sufficient to completely ensure that the pipe does not come out of the joint, especially when the aforementioned sleeve is moulded in plastic and the pipe is also made of plastic.
In these circumstances, it has been found that the teeth tend to slide on the pipe, which can thus, when force is applied, progressively work its way free from the joint.